Process control devices are typically used to control, measure, and/or perform other functions within a process such as opening or closing valves and measuring process parameters. For example, some process control devices may control the pressure of control fluid used to position a pneumatically-controlled device, such as a regulator. For example, an electro-pneumatic controller can be used to control a field device associated with the controller, which may be, for example, valves, valve positioners, switches, transmitters, and sensors (e.g., temperature, pressure, and flow rate sensors). In some forms, these controllers may control the pressure of control fluid into a pneumatic actuator of a process control valve or regulator to position the process control valve or regulator. For example, a valve may open or close in response to a control output received from a controller, or may transmit to a controller a measurement of a process parameter so that the controller can utilize the measurement as a control input. In some cases, the controllers may be used in hazardous environments that are susceptible to damage. Further, the controllers and regulators may use fluids that are flammable or explosive in nature. In such cases, components that may potentially ignite are contained within explosion proof enclosure in order to contain a spark and/or fire therein, thus protecting the installed, potentially flammable environment as well as other control instruments to ensure proper operation.
These enclosures must be properly closed or secured to ensure a proper seal is obtained. Further, such enclosures are not typically intended to allow access to the components contained therein once the enclosure is properly sealed. Some explosion resistant enclosures may be designed according to varying standards that provide a certification that a flame will not propagate to a region outside of the enclosure. Examples of standards include a minimum treacherous path distance and a minimum quantity of engaged threads when the enclosure is secured using fasteners such as bolts and/or screws. In these arrangements, a secondary securing component such as a set screw or other arrangement may be used to prevent the bolt from loosening. However, these secondary securing components may reduce the number of engaged threads in the fastener, which could result in the arrangement no longer adhering to required standards. Additionally, some existing arrangements may resemble other fasteners that are used in process control environments, and as such, operators may inadvertently attempt to gain access to components within the explosion resistant enclosure, and as a result, may adversely impact the ability of the enclosure to contain the spark and/or fire.